In some cases, laser annealing is performed on a semiconductor substrate in order to diffuse and activate an impurity introduced in a semiconductor substrate by ion implantation for example. Patent Literature 1 discloses a laser annealing device having a pulse oscillation laser element which emits pulse laser light and a continuous (or discontinuous) oscillation laser element which emits near-infrared laser light for assisting annealing. This laser annealing device applies pulse laser light after causing the substrate surface temperature to reach a steady state by applying near-infrared laser light. As a result, an impurity existing at substantially large depths in the substrate is activated by securing sufficiently large light-penetration and heat-diffusion lengths.